The MEGX derivatives and analogues of the invention are believed to be new compounds.
It is known that fluorescence polarization immunoassays can be used for determining levels of biologically interesting moieties such as valproic acid in serum, plasma, urine and the like, being disclosed, for example, in U.S. Pat. No. 4,593,089, granted to Wang et al. on June 3, 1986. The patent discloses, by way of example, a method for determining levels of valproic acid in samples which involves mixing with the samples a biologically acceptable salt of 2-ethyl-5-aminopentanoic acid-5-[(4,6-dichlorotriazin-2-yl)-amino]fluorescein conjugate as a tracer, and sheep antiserum to valproic acid as an antibody which recognizes both the valproic acid and the tracer. The valproic acid (a ligand) and the tracer both form complexes with the antibody; the concentrations of tracer and of antibody are both kept constant so that the ratio of ligand-antibody complex to tracer-antibody complex that is formed is directly proportional to the amount of ligand present in the sample. Therefore, upon exciting the mixture with fluorescent light and measuring the polarization of the fluorescence emitted by the tracer and the tracer-antibody complex, it is possible to determine the amount of ligand in the sample by fluorescence polarization techniques.
Fluorescence polarization techniques, as is disclosed in the aforesaid Wang et al. patent, involve determining the polarization of fluorescence of several samples, some known and some unknown, preparing a standard curve showing polarization as a function of concentration from the data for the known samples, and then using the standard curve to determine the concentration of the unknown samples from the measured polarization.
It is also known that certain aminomethylfluoresceins can be used as tracers in using fluorescence polarization techniques to determine levels of biologically interesting moieties such as valproic acid in serum, plasma, urine and the like. By way of example, U.S. Pat. No. 4,510,251, granted to Kirkemo et al. on Apr. 9, 1985, discloses a method for determining levels of estriol and of cortisol in samples which involves mixing with the samples estriol carboxymethyloxime aminomethylfluorescein and cortisol-3-carboxymethyloxime aminomethylfluorescein, respectively, as tracers, and antiserum raised against estriol and antiserum raised against cortisol, respectively, as antibodies, and then determining the amount of tracer-antibody conjugate by fluorescence polarization techniques.
It has also been disclosed (Oellerich et al.: "Monoethylglycinexylidide Formation Kinetics: A Novel Approach to Assessment of Liver Function", J. Clin. Chem Biochem./Vol. 25, 1987/No. 12 pp. 845-853) that fluorescence polarization immunoassay techniques can be used to determine MEGX in serum and in urine, and that measurements of the content of MEGX in serum from venus blood following an intravenous lidocaine bolus (which has the structure of FIG. 2 of the attached drawing) injection can provide a reliable indication of liver function. The reference does not disclose the identity of the reagents used for the immunoassay, stating only that they were provided for investigational use by Abbott Laboratories, the assignee of the subject invention.